The Long Island Central Pine Barrens (LICPB) are one of the few examples of the unique Atlantic coastal pine barrens ecosystem structured by periodic fire disturbance in the eastern United States. Being the home to several endangered and threatened species and overlying the aquifer that supplies Long Island’s drinking water, this ecosystem is protected under the Long Island Central Pine Barrens Protection Act. Nevertheless, forest health and tree population demography in LICPB have been impacted by invasive species, climate change, fire suppression, human development, and a lack of active management. To achieve a better understanding of the trajectory of pitch pine (Pinus rigida) and oak (Quercus alba, Q. coccinea, Q. velutina) populations in both pine- and oak-dominated forest communities on Long Island, we compared their current size-class structure to that documented previously in 2005/2006. We resurveyed 47 of the 93 original 25 x 16 m plots in the summer of 2019 and collected the data on the abundance of trees in five different size classes ranging from seedlings (<0.5 m tall) to canopy trees (>10 cm in diameter at 1.4 m above ground). We used the negative binomial generalized linear model to study changes in tree demography over time.
Results/Conclusions:
Our results suggested that only a few oak and pine seedlings have been recruiting into the next size-class (saplings, 0.5 to 2 m tall) in both pine- or oak-dominated communities, warranting concern for future forest persistence in the area in the absence of fire (which allows recruitment of these species). Importantly, the current size-class structure of both species was very similar to size class structure documented in 2005-2006, suggesting that this lack of recruitment is persistent in the long-term. Since pine seedlings were less abundant than oak seedlings in pine dominated forests, pitch pine forests may transition to oak dominated forests if oak seedlings can recruit to larger size-classes. Our analyses of several plots of relatively recent post-fire origin suggested that fire disturbance increased pitch pine recruitment, corroborating ideas that prescribed burning can be useful as an important management option to bolster pine seedling recruitment in pine-dominated communities. Since plots disturbed by fire are relatively rare on landscapes with the legacy of fire suppression, they are particularly important for our understanding of the dynamics of fire-dependent ecosystems such as pine barrens; consequently, long-term monitoring should take advantage of areas disturbed by fire (prescribed or wildfire).